This application relates to the field of electronic device technologies, and specifically, to a semiconductor device and a preparation method thereof. The semiconductor device includes: a substrate; an epitaxial structure disposed on the substrate; a passivation layer disposed on the epitaxial structure; and an ohmic contact electrode disposed in parallel with the passivation layer on the epitaxial structure, where the ohmic contact electrode includes a non-contact layer and a contact layer that are disposed in a laminated manner, the contact layer is in contact with the epitaxial structure, and composition elements of the contact layer include a germanium element and a tantalum element. The semiconductor device has a low ohmic contact resistance.